DC Generators
Wave winding is composed of

Any odd number of conductors
That even number which is exact multiple of poles + 2
That even number which is exact multiple of poles
Any even number of conductors

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DC Generators
When two D.C. series generators are running in parallel, an equalizer bar is used

To increase the speed and hence generated e.m.f.
To reduce the combined effect of armature reaction of both machines
So that two similar machines will pass approximately equal currents to the load
To increase the series flux

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